1. Field of the Invention
The present invention relates to a carbon nanomaterial manufacturing method in which a tube-shaped material or a fiber-shaped material having carbon as a main constituent is fabricated, a carbon nanomaterial manufacturing apparatus, and a carbon nanomaterial manufacturing facility.
2. Description of the Related Art
In recent years, tube-shaped or fiber-shaped carbon nanomaterials having carbon as the main constituent have become the focus of attention. What have been termed carbon nanotubes and carbon nanofibers are known as examples of this type of carbon nanomaterial.
Among these, carbon nanotubes are tube-shaped carbon polyhedrons having a structure in which graphite sheets are closed into a cylindrical shape. These carbon nanotubes include multilayer nanotubes that have a multilayer structure in which graphite sheets are closed into a cylindrical shape, and monolayer nanotubes that have a monolayer structure in which a graphite sheet is closed into a cylindrical shape.
Multilayer nanotubes were discovered by Iijima in 1991. Specifically, it was discovered that multilayer nanotubes were present in a mass of carbon deposited on a negative electrode used in an are discharge technique. Subsequently, investigations of multilayer nanotubes were aggressively pursued, and in recent years, it has become possible to synthesize multilayer nanotubes in large amounts.
In contrast, monolayer nanotubes have an internal diameter of about 4 to 100 nanometers (nm), and their synthesis was simultaneously reported in 1993 by Iijima and a group at IBM. The electronic state of the monolayer nanotubes was predicted theoretically, and it is thought that the electronic property changes from a metallic character to a semiconductor character due to the manner in which it folds into a spiral. Therefore, this type of monolayer nanotube has promise as a future electronic material.
Other uses of this monolayer nanotubes that can be considered are as nanoelectronic materials, electrolysis electron emitters, a highly aligned radiation source, a soft X-ray source, a one-dimensional conducting material, a high temperature conducting material, and a hydrogen absorbing material. In addition, it is thought that uses of monolayer nanotubes will further spread depending on functional grouping, metallic coating, and incorporation of foreign bodies.
In addition, carbon nanofibers also hold promise in uses such as hydrogen absorbing materials.
Conventionally, the monolayer nanotubes described above are fabricated by incorporating metals such as iron, cobalt, nickel, or lanthanum into a carbon rod and carrying out arc discharge. However, in this method of fabrication, in addition to monolayer nanotubes, multilayer nanotubes, graphite, and amorphous carbon are mixed into the product, and not only is the yield low, but there is variation in both the tube diameter and length of the monolayer nanotubes, and it is difficult to fabricate monolayer nanotubes having comparatively uniform tube diameter and length at a high yield.
Moreover, as a fabrication method for carbon nanotubes, in addition to the arcing method described above, a phase thermal decomposition method, a laser sublimation method, and a condensate phase electrolysis method have been proposed.
As described above, as a fabrication method for carbon nanotubes, the arcing method, the phase thermal decomposition method, the laser sublimation method, and the condensate phase electrolysis method have been proposed.
However, these fabrication methods are fabrication methods that are all at the experimental stage, and in particular, stable mass production is difficult because, for example, the yield of monolayer carbon nanotubes is low and continuous fabrication is not possible.
Thus, being keenly aware about the future possibilities of carbon nanotubes and carbon nanofibers, the development of carbon nanomaterial fabrication methods, carbon nanomaterial fabrication apparatuses, and a carbon nanomaterial fabrication facility is desired that can continuously fabricate carbon nanomaterials that are materials in a tube or fiber shape having carbon as the main constituent, and in particular, carbon materials that include carbon nanomaterials having a high purity, or in other words, can industrially mass produce carbon nanomaterials.
In consideration of the problems described above, it is an object of the present invention to provide a carbon nanomaterial fabrication method, carbon nanomaterial fabrication apparatus, and carbon nanomaterial fabrication facility that can continuously mass produce carbon nanomaterials.